backgroundPositionX not working on Firefox

Question

I have play with youtube\'s sprite animation but there is a problem. backgroundPositionX won\'t work under Firefox (but works on Chrome and IE8)... This is the

Answer 1

Using like this:

background-position: calc(100% - 20px) center; // working on chrome and ff
background-position-x: calc(100% - 20px); // working on ie